[GitHub] [spark] cloud-fan commented on a change in pull request #27444: [SPARK-30614][SQL] The native ALTER COLUMN syntax should change one property at a time

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cloud-fan commented on a change in pull request #27444: [SPARK-30614][SQL] The native ALTER COLUMN syntax should change one property at a time
URL: https://github.com/apache/spark/pull/27444#discussion_r374455848
 
 

 ##########
 File path: sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4
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 @@ -160,7 +160,13 @@ statement
         UNSET TBLPROPERTIES (IF EXISTS)? tablePropertyList             #unsetTableProperties
     | ALTER TABLE table=multipartIdentifier
         (ALTER | CHANGE) COLUMN? column=multipartIdentifier
-        (TYPE dataType)? commentSpec? colPosition?                     #alterTableColumn
+        TYPE dataType                                                  #alterTableColumnType
+    | ALTER TABLE table=multipartIdentifier
 
 Review comment:
   I'd like to make the syntax rule cleaner
   ```
   ALTER TABLE table=multipartIdentifier
     (ALTER | CHANGE) COLUMN? column=multipartIdentifier
     alterColumnAction
   
   alterColumnAction
     : TYPE dataType
     | commentSpec
     | colPosition
     | setOrDrop=(SET | DROP) NOT NULL
   ```

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